Investigating properties of poly (ether‐amide)/MWCNT nanocomposite films containing 2,7‐bis(4‐aminophenoxy)naphthalene and isophthalic segments

Three nanocomposite films based on aramid (poly (ether‐amide), PEA) and multiwall carbon nanotubes (MWCNT) were prepared via solution casting method using 2,7‐bis(4‐aminophenoxy)naphthalene (4) and isophthalic acid (5) containing various amounts of MWCNT (2, 3, 5 wt.%). To comprehensively analyze the properties of the cast films as well as the monomers, different techniques were employed, namely FT‐IR, ¹H NMR, X‐ray diffraction, and field emission scanning electron microscopy. Also, thermal and tensile properties of PEA (6) and nanocomposite films were investigated using thermogravimetric analysis and mechanical analysis, respectively. The morphology, thermal, and mechanical properties of nanocomposite films approved that MWCNT had well dispersion in the PEA matrix and showed a synergistic effect on improving all of the investigated properties. Based on the thermogravimetric analysis results, employing MWCNT caused to increase in the char yields from 61 (in the neat PEA) to 66 (in the PEA /MWCNT nanocomposite 5 wt.%) under the nitrogen atmosphere. In comparison to the pristine PEA (426°C), the temperature at 10 losses mass % (T₁₀) was increased from 530°C to 576°C, with 2 to 5 wt.% of MWCNT. Mechanical analysis revealed that the tensile strength and initial modulus were improved by incorporating MWCNT into PEA (81.70–93.40 MPa and 2.10–2.22 GPa, respectively). Electrical conductivity of the PEA/MWCNT nanocomposites was displayed maximum value in the 5 wt.%, showing satisfactory value in many application areas. The X‐ray diffraction technique was employed to study the crystalline structure of the prepared nanocomposite films as well as PEA. In addition, the electrochemical impedance spectroscopy study demonstrated that the prepared nanocomposites had significant impedance improvement in the presence of MWCNTs.     

UV‐cured polyester‐acrylate nanocomposite films with silane‐grafted silica nanoparticles

UV‐curing technique was employed in this study to prepare polyester‐acrylate nanocomposite films with silane‐grafted silica nanoparticles. Methacryloxypropyl trimethoxysilane was grafted to the surfaces of silica nanoparticles to improve dispersion of silica nanoparticles as well as interfacial adhesion between the resin matrix and silica nanoparticles. The silane‐grafting was confirmed by nuclear magnetic resonance and infrared spectroscopy. The effects of the silane‐grafting on the mechanical and optical properties as well as UV‐curing behavior of the nanocomposite films were investigated. The tensile strength, transmittance, UV‐curing rate, and final chemical conversion of the nanocomposite films were increased by use of the grafted silica nanoparticles as compared to the use of neat silica nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Excellent anti‐bacterial activity and surface properties of polyamide‐6 films modified with argon‐plasma and methyl diallyl ammonium salt‐graft

In this study, the effect of argon‐plasma treatment on the grafting of methyl diallyl ammonium salt (MDAA) onto polyamide‐6 film and the anti‐bacterial and surface properties of the plasma‐ and graft‐treated film were investigated. The grafting amounts of MDAA caused by argon‐plasma treatment increased with the increase in the plasma exposure time and plasma power. The analyses of Fourier transform infrared (FT‐IR) spectroscopy and electron spectroscopy for chemical analysis (ESCA) spectra revealed that the epoxy and vinyl groups of MDAA could be grafted on the argon‐plasma treated polyamide‐6 film. The survey spectra of ESCA, the patterns of atomic force microscopy (AFM), and the spectra from scanning electron microscopy (SEM) were employed to certify the surface modification of argon‐plasma treated and the argon‐plasma treated/MDAA grafted polyamide‐6 films. Argon‐plasma treatment could generate the functional group and increase the roughness on the surface of polyamide‐6 film. This phenomenon could enhance the grafting effect of MDAA. The anti‐bacterial property of argon‐plasma treated/MDAA grafted polyamide‐6 film was excellent. This argon‐plasma treated/MDAA grafted polyamide‐6 film was expected to be applied on the field of packing. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of poly(styrene‐co‐acrylonitrile)‐grafted multiwalled carbon nanotubes via surface‐initiated atom transfer radical polymerization

The in situ grafting‐from approach via atom transfer radical polymerization was successfully applied to polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile grafted onto the convex surfaces of multiwalled carbon nanotubes (MWCNTs) with (2‐hydroxyethyl 2‐bromoisobutyrate) as an initiator. Thermogravimetric analysis showed that effective functionalization was achieved with the grafting approach. The grafted polymers on the MWCNT surface were characterized and confirmed with Fourier transform infrared spectroscopy and nuclear magnetic resonance. Raman and near‐infrared spectroscopy revealed that the grafting of polystyrene, poly(styrene‐co‐acrylonitrile), and polyacrylonitrile slightly affected the side‐wall structures. Field emission scanning electron microscopy showed that the carbon nanotube surface became rough because of the grafting of the polymers. Differential scanning calorimetry results indicated that the polymers grafted onto MWCNTs showed higher glass‐transition temperatures. The polymer‐grafted MWCNTs exhibited relatively good dispersibility in an organic solvent such as tetrahydrofuran. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 460–470, 2007     

Surface amine‐functionalization of UHMWPE fiber by bio‐inspired polydopamine and grafted hexamethylene diamine

Ultrahigh molecular weight polyethylene (UHMWPE) fibers exhibit excellent mechanical property, but their low surface activity limits the application in many fields. In this work, an efficient method was used to improve the surface activity and adhesion property of UHMWPE fibers. The amine functionalized UHMWPE fibers were prepared by the combination of bio‐inspired polydopamine (PDA) and grafted hexamethylene diamine (HMDA). The chemical structure of UHMWPE fibers was characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy. The surface morphologies and mechanical property of the fibers were investigated by scanning electron microscopy and tensile testing respectively. In addition, a single‐fiber pull‐out test was carried out to investigate the adhesion property of the fibers with epoxy resin matrix. The results showed that PDA was coated on the surface of UHMWPE fibers and then HMDA was successfully grafted on the PDA layers. The excellent mechanical property of UHMWPE fibers had no obvious change. Compared with the pristine UHMWPE fibers, the interfacial shear strength of the PDA coated UHMWPE fibers with the epoxy resin matrix improved by 28.3%, while the IFSS of the HMDA grafted UHMWPE fibers had an increase of 82.7%. Copyright © 2017 John Wiley & Sons, Ltd.     

Preparation and characterization of epoxy/SiO2 nanocomposites by cationic photopolymerization and sol–gel process

Epoxy/SiO₂ nanocomposite materials were prepared by cationic photopolymerization and sol–gel process using a novel epoxy oligomer (EP‐Si(OC₂H₅)₃) prepared by 3‐isocyanatopropyltriethoxysilane (IPTS)‐grafted bisphenol A epoxy resin and tetraethyl orthosilicate as inorganic precursor. The chemical structures of EP‐Si(OC₂H₅)₃ were characterized by Fourier transformed infrared spectroscopy. Transmission electron microscopy showed that the in situ generated nano‐SiO₂ dispersed uniformly in the EP matrix, and its average diameter is around 40 nm. The relationship between nanocomposite materials' thermal/mechanical properties and nano‐SiO₂ introduced were studied by thermogravimetric analysis, dynamic mechanical analysis, and impact strength test. The results showed that the nanocomposite materials' thermal and mechanical properties improved a lot with increase of the SiO₂ content. Copyright © 2013 John Wiley & Sons, Ltd.     

Improved mechanical properties of epoxy‐based composites with hyperbranched polymer grafting glass‐fiber

A glass‐fiber, grafted by hyperbranched polymer with hydroxyl group (GF‐HBPH), reinforced epoxy‐based composite was evaluated for mechanical properties and compared with the neat epoxy and silanized glass‐fiber, GF‐APS. The epoxy/GF‐HBPH composites were studied by attenuated total internal reflectance infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, mechanical properties analysis, and field emission‐scanning electron microscopy. The results showed that the incorporation of GF‐HBPH could simultaneously enhance the mechanical properties of the epoxy composites. Field emission‐scanning electron microscopy images of the fracture surfaces of the test specimens were used to support the results and conclusions. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and morphological,electrical, and mechanical properties of polyimide‐grafted MWCNT/polyimide composite

Precursor of polyimide, polyamic acid has been prepared sucessfully. Acid‐modified carbon nanotube (MWCNT) was grafted with soluble polyimide then was added to the polyamic acid and heated to 300 °C to form polyimide/carbon nanotube composite via imidation. Morphology, mechanical properties and electrical resistivity of the MWCNT/polyimide composites have been studied. Transmission electron microscope microphotographs show that the diameter of soluble polyimide‐grafted MWCNT was increased from 30–60 nm to 200 nm, that is a thickness of 70–85 nm of the soluble polyimide was grafted on the MWCNT surface. PI‐g‐MWCNT was well dispersed in the polymer matrix. Percolation threshold of MWCNT/polyimide composites has been investigated. PI‐g‐MWCNT/PI composites exhibit lower electrical resistivity than that of the acid‐modified MWCNT/PI composites. The surface resistivity of 5.0 phr MWCNT/polyimide composites was 2.82 × 10⁸ Ω/cm² (PI‐g‐MWCNT) and 2.53 × 10⁹ Ω/cm² (acid‐modified MWCNT). The volume resistivity of 5.0 phr MWCNT/polyimide composites was 8.77 × 10⁶ Ω cm (PI‐g‐MWCNT) and 1.33 × 10¹³ Ω cm (acid‐modified MWCNT).Tensile strength and Young's modulus increased significantly with the increase of MWCNT content. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3349–3358, 2007     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Quantitative analysis of MWCNT agglomeration in polymeric‐based membranes using atomic force microscope

In this work, we performed an analysis on the surface properties of polyethersulfone (PES)‐based ultrafiltration membranes that were prepared by incorporating acid functionalized multiwalled carbon nanotube (f‐MWCNT) and polyvinylpyrrolidone into membrane matrix via simple blending method. The bonding‐chemistry of the nanocomposites implanted within the PES membrane was investigated by Fourier transform infrared spectrometer while atomic force microscope was employed to observe the distribution of f‐MWCNT in the membrane matrix and further measured its agglomeration quantitatively. The resultant 3D atomic force microscope images provided the most satisfactory way to examine the distribution of nanomaterials in the membranes, and with the help of ‘point profile data’ the maximum height and width of the agglomerated cluster could be quantitatively calculated. Moreover, the surface profile studies of the membrane surface provided the information about the length, volume, area, perimeter, radius and diameter of grains. It was observed that PES/nanocomposite blended membranes were held together via strong hydrogen bonding, but poor dispersion of MWCNT in the membrane matrix reduced the membrane performance in terms of protein (pepsin and bovine albumin serum) rejection and increased the surface roughness. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and studies of thermal,mechanical and electrical properties of MWCNT–cyclodextrin as a nanoparticle in polyamide matrix based on 2,2‐Bis[4‐(4‐aminophenoxy)phenyl] propane

In the present research, polyamide (PA) ( 6 ) was synthesized by the polycondensation reaction of 2,2‐Bis[4‐(4‐aminophenoxy)phenyl] propane as a diamine ( 4 ) with adipic acid ( 5 ) in the optimized condition. The resulting PA was characterized using Fourier transform infrared spectroscopy, Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy, inherent viscosity (η_inh), X‐ray diffraction, and solubility tests. Also, the thermal property of the new PA ( 6 ) was investigated by using Thermogravimetric analysis. To apply multiwall carbon nanotube (MWCNT) as an effective reinforcement in polymer composites, it is essential to have appropriate proper dispersion, interfacial adhesion between the MWCNT and polymer matrix, and increasing solubility. With this end particularly, functionalized MWCNTs were combined with a soluble molecule, and a series of modified MWCNT with cyclodextrin (Cy) known as PA/MWCNT‐Cy composite film (2, 5, and 8 wt%) were prepared by a solution intercalation technique. Field emission scanning electron microscopy images showed that MWCNT‐Cy was well dispersed in the PA matrix. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared with the pristine PA. Anisotropic structure of the synthesized films and dispersed MWCNT‐Cy in the films approved by use of X‐ray diffraction and field emission scanning electron microscopy. The resultant PA/MWCNT‐Cy composite films were electrically conductive, which is favorable for many practical uses. Measurements of mechanical properties of these composite films showed high strength in 8% MWCNT‐Cy content. Also, results showed increases in Young's modulus and tensile strength. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface modified multi‐walled carbon nanotubes and Nafion nanocomposite membranes for use in fuel cell applications

The preparation and characterization of the nanocomposite polyelectrolyte membranes, based on Nafion, sulfonated multi‐walled carbon nanotubes (MWCNT‐SO₃H) and imidazole modified multi‐walled carbon nanotubes (MWCNT‐Im), for direct methanol fuel cell applications is described. The results showed that the modification of multi‐walled carbon nanotubes (MWCNT) with proton‐conducting groups (sulfonic acid groups or imidazole groups) could enhance the proton conductivity of the nanocomposite membranes in comparison to Nafion 117. Regarding the interactions between the protonated imidazole groups, grafted on the surface of MWCNT, and the negatively charged sulfonic acid groups of Nafion, new electrostatic interactions can be formed in the interface of the Nafion and MWCNT‐Im, which result in both lower methanol permeability and higher proton conductivity. The physical characteristics of these manufactured nanocomposite membranes were investigated by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, water uptake, methanol permeability, and ion exchange capacity, as well as proton conductivity. The Nafion/MWCNT‐Im membranes showed the higher proton conductivity, lower methanol permeability, and, as a consequence, a higher selectivity parameter in comparison to the neat Nafion or Nafion membrane containing MWCNT‐SO₃H or ─OH functionalized multi‐walled carbon nanotubes (MWCNT‐OH) membranes. The obtained results indicated that the Nafion/MWCNT‐Im membranes could be used as efficient polyelectrolyte membranes for direct methanol fuel cell applications.     

Preparation and enhanced properties of poly(propylene)/ silica‐grafted‐hyperbranched polyester nanocomposites

A series of poly(propylene) silica‐grafted‐hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn? H20), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface of SiO₂ particles (30 nm) through 3‐glycidoxy‐propyltrimethoxysilane (GPTS) was prepared. The effect of silica‐grafted‐modified Boltorn? H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn? H20 was successfully grafted onto the SiO₂ surface confirmed by FT‐IR and X‐ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica‐grafted‐modified Boltorn? H20 (3–5 wt% SiO₂) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica‐grafted‐modified Boltorn? H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica‐grafted‐modified Boltorn? H20 particles were added compared with PP/SiO₂ or PP/SiO₂‐GPTS composites. Copyright © 2004 John Wiley & Sons, Ltd.     

接枝共聚法制备二氧化钛/聚（苯乙烯-二乙烯基苯）复合微球

本文以KH560、苯乙烯、马来酸酐为连接组分,将二氧化钛接枝到聚（苯乙烯-二乙烯基苯）微球的表面,成功制备了无孔和多孔纳米复合微球。研究了硅烷偶联剂（KH560）和苯乙烯对二氧化钛在无孔微球表面的分散性和接枝数量以及支撑微球的多孔性质对接枝到微球内部的二氧化钛数量的影响。结果表明,KH560和苯乙烯能够提高二氧化钛在微球表面的分散性和稳定性,使二氧化钛以30-80nm的粒径接枝在微球表面。苯乙烯又能使二氧化钛在无孔微球表面的接枝数量从10.4%增大到20.4%。平均孔径为136nm的多孔微球为支撑微球得到的复合粒子中二氧化钛最高接枝量可达26%,明显高于无孔微球和平均孔径为31nm的多孔微球。     

Synthesis and optoelectronic behavior of conjugated polymer poly(3‐hexylthiophene) grafted on multiwalled carbon nanotubes

A nanocomposite of multiwalled carbon nanotubes (CNTs) and poly(3‐hexylthiophene) (P3HT) was prepared by grafting P3HT uniformly on the surface of CNTs (P3HT/P3HT‐g‐CNT) via a “grafting from” method with the coating thicknesses controlled. It was found that as the coating thickness decreased, the crystallinity of the P3HT decreased, along with significant red‐shifting of Raman that signified alterations of chain conformation. Furthermore, although the photoluminescence (PL) peak remained unchanged when grafted on CNTs, modifications of P3HT energy gap was observed, indicating variations of vibronic levels arising from the grafting. Moreover, broadening of the PL emission took place that suggested decreasing of lifetimes of the photo‐generated species when grafted on CNTs. Bilayer photovoltaic devices with the (6,6)‐phenyl C61‐butyric acid methyl ester as the electron acceptor have shown that the nanocomposite P3HT/P3HT‐g‐CNT performed much more efficiently as the electron donor, in both photocurrent density and power conversion efficiency, compared with the neat P3HT. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Poly(vinyltriethoxysilane) modified MWCNT/polyimide nanocomposites—Preparation,morphological, mechanical,and electrical properties

Multi‐walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES‐MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4′‐oxydianiline with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride. PVTES‐MWCNT were then mixed with polyamic acid and heated to 300 °C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (Si? O? Si). The PVTES‐MWCNT was analyzed by Fourier transform infrared and X‐ray photoelectron spectroscopy. The PVTES‐MWCNT/polyimide composites were analyzed by CP/MAS solid state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES‐MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES‐MWCNT. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 803–816, 2008     

Comparative study on the properties of poly(trimethylene terephthalate) ‐based nanocomposites containing multi‐walled carbon (MWCNT) and tungsten disulfide (INT‐WS2) nanotubes

Multi‐walled carbon (MWCNT) and tungsten disulfide (INT‐WS₂) nanotubes are materials with excellent mechanical properties, high electrical and thermal conductivity. These special properties make them excellent candidates for high strength and electrically conductive polymer nanocomposite applications. In this work, the possibility of the improvement of mechanical, thermal and electrical properties of poly(trimethylene terephthalate) (PTT) by the introduction of MWCNT and INT‐WS₂ nanotubes was investigated. The PTT nanocomposites with low loading of nanotubes were prepared by in situ polymerization method. Analysis of the nanocomposites' morphology carried out by SEM and TEM has confirmed that well‐dispersed nanotubes in the PTT matrix were obtained at low loading (<0.5 wt%). Thermal and thermo‐oxidative stability of nanocomposites was not affected by the presence of nanotubes in PTT matrix. Loading with INT‐WS₂ up to 0.5 wt% was insufficient to ensure electrical conductivity of PTT nanocomposite films. In the case of nanocomposites filled with MWCNT, it was found that nanotube incorporation leads to increase of electrical conductivity of PTT films by 10 orders of magnitude, approaching a value of 10^?3 S/cm at loading of 0.3 wt%. Tensile properties of amorphous and semicrystalline (annealed samples) nanocomposites were affected by the presence of nanotubes. Moreover, the increase in the brittleness of semicrystalline nanocomposites with the increase in MWCNT loading was observed, while the nanocomposites filled with INT‐WS₂ were less brittle than neat PTT. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal,physico‐mechanical,and morphological properties of HDPE graft‐copolymerized with polystyrene

In this study, polystyrene was graft‐copolymerized onto high‐density polyethylene (HDPE) by in situ polymerization of styrene monomer to change the physico‐mechanical and thermal properties of HDPE. The grafting was carried out in a Brabender‐type static mixer by injecting styrene monomer directly into the molten HDPE in the presence of a free‐radical initiator (lauroyl peroxide or LP). The effect of wt% of styrene and initiator concentrations on thermal, physico‐mechanical, and morphological properties of HDPE was investigated. The neat and modified HDPE was characterized by differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and also by tensile strength and contact angle measurements. It was found that the increase in wt% of styrene and LP dosage reduced elongation at break, hygroscopic expansion and also the melting, and the crystallization temperatures of HDPE but increased its tensile strength. The tensile strength was increased from 14.6 MPa for the neat HDPE to 20.6 MPA for the 10 wt% of styrene grafted onto HDPE using 0.8% LP. Scanning electron microscopy results show that there was no phase separation, and the grafted polystyrene became integral part of HDPE. The results demonstrate that styrene could be used in melt compounding to improve various properties of HDPE. Copyright © 2015 John Wiley & Sons, Ltd.     

Composites of poly(L‐lactide‐trimethylene carbonate‐glycolide) and surface modified SBA‐15 as bone repair material

This work aims to develop novel composites from a poly(L ‐lactide‐co‐trimethylene carbonate‐co‐glycolide) (PLTG) terpolymer and mesoporous silica (SBA‐15) nanofillers surface modified by post‐synthetic functionalization. SBA‐15 first reacts with a silane coupling agent, γ‐aminopropyl‐trimethoxysilane to introduce ammonium group. PLLA chains were then grafted on the surface of SBA‐15 through ammonium initiated ring‐opening polymerization of L ‐lactide. Composites were prepared via solution mixing of PLTG terpolymer and surface modified SBA‐15. The structures and properties of pure SBA‐15, γ‐aminopropyl‐trimethoxysilane modified SBA‐15 (H₂N‐SBA‐15), PLLA modified SBA‐15 (PLLA‐NH‐SBA‐15), and PLTG/PLLA‐NH‐SBA‐15 composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, N₂ adsorption‐desorption, differential scanning calorimetry, contact angle measurement, and mechanical testing. The results demonstrated that PLLA chains were successfully grafted onto the surface of SBA‐15 with grafting amounts up to 16 wt.%. The PLTG/PLLA‐NH‐SBA‐15 composites exhibit good mechanical properties. The tensile strength, Young's modulus, and elongation at break of the composite containing 5 wt.% of PLLA‐NH‐SBA‐15 were 39.9 MPa, 1.3 GPa, and 273.6%, respectively, which were all higher than those of neat PLTG or of the composite containing 5 wt.% of pure SBA‐15. Cytocompatibility tests showed that the composites present very low cytotoxicity.     

Radiation‐grafted solid polymer electrolyte membrane: studies of fluorinated ethylene propylene (FEP) copolymer‐g‐acrylic acid grafted membranes and their sulfonated derivatives

Acrylic acid was grafted onto FEP by simultaneous radiation technique and the resulting membranes were sulfonated. Results of dynamic mechanical properties of the membranes showed that storage modulus and temperature at tan δ_(max) increases on grafting. X‐ray diffraction (XRD) analysis of the grafted and sulfonated membranes showed decreasing trend in crystallinity with increase in degree of grafting. From scanning electron microscopy (SEM) studies it was confirmed that grafting takes place by the front mechanism. Copyright © 2004 John Wiley & Sons, Ltd.